1. Field of the Invention
The present invention relates to micro oscillating devices such as micromirror devices, acceleration sensors, angular-speed sensors and vibration devices which have tiny moving parts or oscillating parts. The present invention also relates to-micro oscillating device arrays.
2. Description of the Related Art
In recent years, efforts are being made in many technical fields for making practical application of devices which have a micro-structure formed by micromachining technology. Such devices include micromirror devices, acceleration sensors, angular-speed sensors and other micro oscillating devices which have tiny moving parts or vibrating parts therein. Micromirror devices are used in the field of optical disc technology and optical communications technology for example, as a light reflection device. Acceleration sensors and angular-speed sensors find their ways in the field of correction of camera shake in video cameras and cameras incorporated in mobile telephones, car navigation systems, air bag release timing control system, attitude control of automobiles and robots, and so on. These micro oscillating devices generally include a fixed part, a moving part, and a connecting part which connects the fixed part and the moving part. These micro oscillating devices are disclosed in JP-A-2003-19700, JP-A-2004-341364, and JP-A-2006-72252, for example.
Micro oscillating devices often uses, as their driving mechanism, an electrostatic actuator for generation of a driving force. The driving force is provided by an electrostatic attraction when a voltage is applied between a pair of electrodes. A problem with the electrostatic actuator is that when the voltage is applied, an electric field formed by the electrode pair can leak out of the actuator. It has been known that the electric field leakage is apt to occur in comb-teeth type electrostatic actuators for example.
In a case where two micro oscillating devices are placed closely to each other, electric field leakage from one electrostatic actuator can cause an adverse affect to the drive characteristic of the adjacent micro oscillating device. For example, in a micromirror device array which includes a plurality of micromirror devices, i.e. micro oscillating devices, which are laid in one-dimensional or two-dimensional manner, electric field leakage from the electrostatic actuator of one micromirror device can cause an adverse affect to the drive characteristic of other, adjacent micro oscillating devices. In order to eliminate the adverse affect to the drive characteristic caused by the electric field leakage in micromirror device arrays (micro oscillating device arrays), the micromirror devices (the micro oscillating devices) must be spaced from each other by a sufficiently large pitch. In other words, electric field leakage is a problem in an effort for increased device density in the micro oscillating device arrays.